Relay



Nov. 8, 1938. E. o. BLODGETT RELAY Filed July 28, 1934 5 $heetsSheet l FIG-.1.

17 as a? 2434 N V E m M V ATTORNEY Nov. 8, 1938. I E, BVLODGETT 2,135,490

RELAY Filed July 28, 1934 3 Sheets-Sheet 2 |||IT 55 [mill] 11 4 2: I I E 20 19 19 22 22 18 :2

2 1 2 2a 9 275/121; 45\50 Q 10 2a 25 27 INVENTOR 5.0. M!

ATTORNEY Patented Nov. 8, 1938 PATENT OFFICE RELAY Edwin 0. Blodgett, Rochester, N. 'Y., assignor to General Railway Signal Company, Rochester,

Application July 28, 1934, Serial No. 737,440

24 Claims.

This invention relates to relays, and more particularly to a tractive type relay which is selfcompensating to allow its armature to be released from its attracted position in response to anabrupt decrease in energization of the relay with the same certainty regardless of the degree of energization which had gradually obtained previously In a normally energized track circuit, it is essential to attract the armature of the track relay associated therewith and to hold the armature in its attracted position during normally unoccupied conditions from current passing through the rails of the insulating section of trackin series, but when the section becomes occupied, the train must shunt suificient current through the wheels and axles to effect the release of the relay armature. Obviously, then, the leakage of the current from one rail to the other throughout the track section affects the armature of the track relay in the same manner as the shunt effected by a train, and consequently it is found that when the track circuit current is adjusted to a .value permitting proper operation at any one time, a change in weather condition may in one instance sufliciently, increase the current leakage between rails to duplicate the effect of a train shunt and drop the usual type of track relay, or in another instance the leakage current may sufficiently decrease to increase the relay energization to such an abnormally high value that the relay armature will not release in response to a train shunt.

In view of the above and other considerations,

it is proposed in accordance with the present invention to provide a self-compensating relay particularly adapted to produce reliable operationunder various special conditions, such as encountered in a track circuit, to which the conventional type of tractive relay is not particularly adapted. Specifically, it is proposed to provide a relay of the tractive armature type which is self-compensating to maintain a constant tractive force acting on its armature when in its attracted position regardless of changes which occur gradually in the energization ofv the relay to thereby allow the armature to drop away in response to an abrupt reduction in energization with equal certainty regardless of the degree of e-nergization which had previously obtained gradually. It is further proposed to provide a locking means actuated by a release of the armature to prevent the above compensating action as longas the armature is in its released position, and it is also proposed to incorporate a simple and reliable means for manually adjusting the magnitude of the armature retaining force'which is to thus be maintained constant regardless of subsequent gradual variations in energization, and to provide such an adjustment which will not afiect the magnitude of the force by which the armature is attracted from its released position.

Other objects, purposes and characteristic features of the present invention will be obvious as the description thereof progresses, during which, references will be made to the accompanying drawings, in'which Fig. 1 diagrammatically shows a preferred form of the present invention applied to a normally energized railway track circuit.

Fig. 2 is a front elevational sectional view of a relay incorporating a preferred embodiment of the present invention.

Fig. 3 is a side elevational sectional View of the relay shown in Fig 2.

Fig. 4 is a partial bottom View of the relay shown in Fig. 2 with the armature and certain other parts removed. 7

Fig. 5 is a plan view of a detail of the relay shown in Fig. 2.

Fig. 6 is a partial front elevational sectional view showing a modification which may be made in the relay shown in Fig. 2.

Fig. '7 is a side elevational view of a relay incorporating a modified form of the present invention with certain parts of the relay sectioned and other parts removed.

Fig. 8 is a front elevational view of the relay shown in Fig. 7, also having certain parts sectioned.

In the drawings the present invention has been shown as applied to a relay constructed along the lines of the type found suitable for 40 railway signalling systems and particularly for railway track circuits, but it will be obvious that the present invention can equally well be applied to various other well known relay types. The general construction of the relay shown in detail includes two vertical cores 1 and 8 having enlarged lower ends forming pole faces 9 and Ill, respectively, whereby they are held to a top plate II by screws l2, the top plate it being of insulating or at least non-magnetic material. The cores 1 and 8 carry windings I3 and M, respectively, which are normally connected in series and arranged to produce cumulative flux within the cores 1 and 8, which cores are joined at their upper ends by a yoke l5 of magnetic material held thereto by bolts I6.

A tractive type magnetic armature I1 is pivotally supported below the lower surface of the pole pieces 9 and It so as to be attracted thereto and complete the magnetic circuit by energization of the coils I3 and M, the armature ll being biased away from the pole pieces 9 and ill by gravity. The armature supporting means Boomprises a non-magnetic yoke l8 (see Fig. 4) suspended from the top plate II by bolts l9 each attached to the top plate II by nuts 20 bearing on spacing bushings 2|, the yoke l8 being carried between upper and lower nuts 22 .to thereby be vertically adjustable along the end portions of the bolts 19. Two armature arms 23 are suitably attached to the armature H and adjustably hold outwardly extending trunnion pins 25 by screws 26, which trunnion ,pins have reduced ends rotatably fitting into holes in. downwardly extending lugs 21 carried by the yoke I8. The armature :l"! is thus adjustably supported to permit pivotal movement relative to the pole faces 9 and ID with a minimum of friction.

Suitable contacts are, of course, attached to the armature I! in a manner to engage either upper or lower fixed contacts in. accordance with the operation of the armature, but to simplify the present disclosure such contact means have been omitted from all views, except Fig. 3 which shows in a very diagrammatic manner a movable contact finger 28 attached to the armature I! by insulating spacing screws ,29, and this movable finger 28 engages either front or back fixed contacts indicated merely by the arrows in.

Fig. 3.

In a tractive type relay, such as just described, it is well known that the force retaining the armature in its attracted position against the pole pieces is substantially proportional to the flux in the magnetic circuit, and consequently in certain relay applications, such as, a track circuit wherein it is desirable to maintain 'a constant armature retaining force when the track section is unoccupied, it is desirable to maintain the flux in the magnetic circuit constant regardless of changes in intererail leakage current. A constant flux Value can, of course, be maintained by an auxiliary means maintaining a constant value of energization of the relay coils or the magnetomotive force of the relay but the present device does not act on the energizing circuit but rather, it acts on the magnetic circuit in a manner to maintain a constant flux value in the magnetic circuit by varying the reluctance thereof in inverse proportion to changes in the magnetomotive force which occur gradually, and yet allow the flux to decrease sufficiently in response to abrupt changes in the magnetomotive force to release the armature.

Inasmuch as one factor determining the reluctance of the magnetic circuit is the air gap separating the armature from the pole faces, the present device is arranged to enforce a separation of the armature H from the pole faces 9 and it which is in inverse proportion to the magnetomotive force obtaining between these pole pieces 9 and Ill. The preferred apparatus for effecting such operation is shown in Figs. 2 to 5 inclusively, and comprises a vertical shaft 33 positioned midway between the cores 1 and 8 with its lower end rounded and engaging the upper surface of the armature I! and its upper end threaded into a bushing 34. The bushing 34 is shown as threaded only at its upper end, the lower end forming a bearing for the shaft 33 andis provided with an annular upper flange retained in a recess in the top of the plate H by a cover plate 35 secured above the plate H by screws 36 as shown in Fig. 5.

The shaft 33 is rotated to various positions in accordance with the magnetomotive force obtaining between the pole pieces 59 and I'll by an armature 31 suitably attached thereto and hav' flux flowing therethrough from one pole piece to the other, .and of course, the armature 3] also tends to rotate to a position wherein the :reluctance to the flow of such flux therethrough is a minimum or, that is, to place more of the surface of its pole faces in register with the surface .of the pole pieces 9 and 10., all .of which is .in accordance with well known principles of magnetic attraction.

Referring to Fig. l which is a view looking at the lower end of the present relay with the armature I! removed, the rotatable armature 31 is shown as rotated to its extreme position .in a

rcounter-clockwi'se direction against the biasing force of a spiral coil spring :38, which spring is attached at its inner end to the top plate I I by a stud 39, and at its other end to :a sector 40 by a pin ll. The sector '40 "is also attached to the shaft 33 at a point above the armature .31 and extends rearwardly for a purpose to be later described.

If the spring '38 is arranged to exert a force tending to rotate the shaft 133 in a clockwise direction which force increases evenly in direct proportion to the counter-clockwise rotation of the .shaft 33, the various values of magnetomotive force between the pole pieces 9 .and Ill will effect a force counteracting the opposing force of the spring 38 only at certain definite rotated positions of the shaft 33. For example, when the armature 31 is in the position shown, each decrement in the magnetomotive force produces a proportional degree of clockwise rotation of the shaft 33. Inasmuch as the upper end of the shaft 33 is provided with right-hand threads, the shaft will now be moved upwardly within the stationary threaded bushing '34 due to this clockwise rotation, thereby allowing the armature H to move closer 'to'the pole pieces 9 and 13 This upward movement of the armature I! as permitted by the upward movement of the shaft 33 obviously decreases the air gap between the armature H and the pole pieces 9 and I0, thereby decreasing the reluctance of the magnetic circuit in direct proportion to the'degree of reduction in energization of'the coils l3 and M as detected by the rotation of the armature 31. In this manner, the flux in the armature l? and consequently the tractive force acting thereon is maintained at a constant value regardless of the decrease in the magnetomotive force or the energization of the relay coils I3 and I4. I

The converse action of the armature 31 is of course obvious, or that is, the shaft 33 will be rotated counterclockwise in response to a gradacteristics of the magnetic circuit and on the proportion of various other parts of the relay,

but it is to be understood that these threads must be arranged to vary the air gap between the armature I I and the pole pieces 9 and I0 in such a proportion to a change in magnetomotive force that the flux in the armature II remains at a constant value.

a It was previously mentioned that the armature '3'! is to respond only to changes which occur gradually in the magnetomotive force or the energization of coils I3 and I4, and the air gap should'not be varied in response to an abrupt decrease in relay energization. This is because the purpose of regulating the air gap is to allow the armature to at all times drop away with equal certainty when the energization is quickly reduced, and if the air gap were varied in response to this quick reduction before the -armature dropped away, the benefit of the previous air gap regulation would be lost.

Consequently, the armature 31 is provided with two flux retarding washers or slugs 43 of a nonmagnetic current-conducting material, such as copper, brass or aluminum, and these slugs 43 completely surround'the armature 31 at positions between the shaft 33 and the respective enlarged ends or pole faces. An effective amount of current is then induced in these Washers 43 when the flux in the armature 37 tends to change quickly, which current acts to retard such change influx in a manner which is well recognized in the relay art. These slugs 43 will then act to retard a rapid decrease in flux in the armature 3'! in response to a rapidly reduced relay energization, thereby preventing an effective rotation of the armature 37 until the armature IT has been released by the reduction of the flux permitted by the inaction of the armature 37. However, gradual changes in the relay energization or the magnetomotive force will produce such a gradual flux change through the armature 3'! that the flux retarding slugs 43 are practically ineffective, and the rotation of the armature 31. will follow very closely such gradual changes in magnetomotive force.

It is to be understood, however, that although the armature Il drops away before the armature 31 can respond to a rapidly reduced value of magnetomotive force, the armature 31 will sub-- sequently respond to this reduced value by rotating to a position moving the shaft 33 downwardly. However, when the armature I1 is again attracted by a quickly increased value of magnetomotive force, the armature 3'! will not immediately rotate back to again raise the shaft 33, and during the operation of the armature 3'! an air gap will be momentarily provided which isn'ot proportional to the newly increased magnetomotive force.

In some applications such operation of the armature 3'! while the armature I1 is released, may be objectionable, and consequently the present relay is provided with an upwardly extending spring arm 44 suitably attached to a rearwardly extending bracket 45 fixed to the armature I1 by screws 46 as shown in Fig. 3. The upper end of the spring arm 44 is positioned slightly to the rear of and out of engagement with the edges of the previously mentioned sector 40 when the armature I1 is attracted, but when the armature I! is released, the spring arm 44 is operated forwardly to engage the edge of the sector 40 and thereby prevent further movement of the shaft 33 while the armature I1 is in its released position.

Inasmuch as it has been considered that the rotation of the shaft 33 will not be more than about one-fourth of a revolution, the sector 43 may have a quarter circular outer edge concentric with the shaft 33 as shown in Fig. 4, and the right-hand edge may form a stop for the biased direction of rotation by engaging the downwardly extending head of the spring holding stud 39. The outer edge of the sector 40 may be roughened or serrated to provide a better frictional contact with the spring arm 44.

The present device, of course, necessitates that the normal or average energization of the coils I3 and I4 be adjusted to a value which reliably attracts the armature I I from its deenergized position, and low enough to permit reasonably gradual variations either above or below this normal value to fall within the range of operation of the armature 31 in order to maintain a constant flux in the armature El. This constant armature flux must also be of a value which permits the most reliable armature release in response to the degree of abrupt reduction in the energization of coils I 3 and I4 which is effected in the particular circuit application.

However, it is found in certain applications, such as railway track circuits, that even though the normal or average energization of the relay coils is a correct value, the abrupt reductions in energization may be of considerably different magnitudes in different track circuits, due perhaps to the different weights of trains shunting the track circuits, and the like. It then becomes desirable that this constant flux value in the armature I I be adjusted to a value providing proper armature release in response to the degree of the abrupt energy reduction resulting from the particulartrain shunts, providing such adjustment does not affect the degree of energization required to pick up the armature.

A rather simple means has consequently been provided for manually adjusting the normal or average air gap between the pole pieces 9 and I0 and the armature I I when attracted, to thereby select a normal flux value in the armature I? which provides the maximum reliability of response to the particular abrupt reduction of relay energization effected in each application.

This means is shown in Fig. 5 as comprising a pointer arm 48 extending forwardly from the flange of the bushing 34 and having a pointer at its front end cooperating with arcuate graduations suitably marked on the top plate I I. The arm 48 may be rotated in either direction from its illustrated position thus rotating the bushing 34 relatively to the shaft 33 to either move the shaft 33 upwardly or downwardly to accordingly vary the air gap between the armature I1 and the pole pieces 9 and I0, and consequently vary the normal value of flux in the armature IT. The adjusted position of the arm 48 may be retained by a screw 49 threaded into the top plate II and extending through a circular slot in the outer end of the arm 48.

In Fig. 6 of the drawings, the same relay as shown in Fig. 2 is illustrated as having windings 59 on the rotating armature 31 in addition to the non-magnetic current-conducting washers 43, which washers in this case, are made shorter to provide space for the coils 59. The two windings 5B are shown as connected in series by a wire 5| and in multiple with the main windings I3 and I4 by wires 52, and these windings 50 are arranged to produce cumulative flux in the armature 31, which fiux is to flow in the same direction as the flux produced in the armature 31 by energization of coils l3 and M. This arrangement in Fig. 6 substantially constitutes a shunt motor mechanism for rotating the shaft 33, wherein the windings l3 and M supply the field excitation coacting with the armature flux supplied by windings 59, and it is contemplated that additional torque tending to rotate the shaft 33 throughout its 90 degree rotation against the biasing spring 38 may thereby be provided. The washers 43 are intended to retard the response of the armature 31 to rapid changes in energization of the relay in the same manner as in Fig. 2.

The operation of the previously described form of the present relay may be more clearly set forth by referring to Fig. l, in which a very diagrammatic representation of the preferred form of the present invention is shown connected across one end of two track rails T, the other rail ends being connected to a battery B in series with a manually adjustable resistor R to thereby normallyenergize the windings of the present relay by current from .the battery B flowing through the track rails T in series. The parts of the present relay which are diagramatically shown in Fig. l have been given the same reference characters as assigned to the represented parts of the specific construction already described, and obviously this track circuit current flows through windings l3 and I4 to attract and hold the armature IT in its upper position, which current is adjusted by the variable resistor R to provide .a predetermined desired value of magnetomotive force which is suflicient to easily attract the armature I! under normal or average leakage current through the ballast separating the rails T when not shunted by a train.

The manually adjusting arm 48 (not shown in Fig. 1) is now also adjusted to allowa flux value in the armature I! in response to this adjusted value of magnetomotive force, which produces a tractive force reliably retaining the armature I! in its attracted position, but which permits the reduction in magnetomotive force effected by the train shunt obtaining on the particular track section to reduce this flux value considerably below the value at which the relay armature l I is found to drop away. In other words, the means for manually adjusting the air gap normally separating the armature I! from the pole pieces 9 and l 0 provides a simple and convenient means for adjusting the release value of the relay armature without affecting the pick-up value.

When the inter-rail leakage current changes in the track circuit of Fig. 1, due, for example, to weather changes, the changes in relay energization resulting therefrom occur gradually and the armature 37 rotates in a corresponding direction accordingly, thereby increasing or decreasing the reluctance of the magnetic circuit in inverse proportion to the change in magnetomotive force produced by the change in energization to maintain a constant flux, and obviously a constant tractive force acting on the armature I! in the manner previously described. However, when the train enters the track section to shunt the rails T, the energization of the relay coils l3 and I4 is quickly decreased, and inasmuch as the compensating armature 31 is retarded by the washers 43 (not shown in Fig. l) the flux decreases in the armature I! beyond a point where the retaining force is overcome by the gravitational biasing force and thearmature I I immediately drops away. The dropping of the armature I1 then engages the arm 44 with the sector 49 and prevents movement of the compensating armature 31 as long as the track rails T are shunted. It may be mentioned that this means for preventing the operation of the compensating armature 31 while the armature I! is released may be omitted from the present devices and yet retain the most desirable operating characteristics, but in order to prevent unnecessary operation of armature 31 as previously outlined, its incorporation is considered advantageous. 7

An air gap compensating means is thus provided which operates to maintain a constant force retaining the armature IT in its attracted position regardless of various gradual changes in the energization of the relay. This arrangement then insures that the relay armature releases in response to a rapid reduction of energization with the same certainty regardless of the degree of energization of the relay coils which had prevailed before the rapid energy reduction.

In the .modified form of the present invention shown in Fig. 7 and Fig. 8, substantially the same main magnetic structure has been shown in order 7 to simplify the disclosure, but the mechanical construction of the compensating means is entirely different although the principle of operation is substantially the same. The specific construction in Fig. 7 and Fig. 8 comprises a horizontal magnetic shaft 55 rotatably supported in front of the pole pieces 9 and ID by two brackets 56 fixed to the top plate I I by bolts 5'! and nuts 58, which brackets 56 carry threaded pins 59 having reduced ends entering holes in each end of the shaft'55, as shown in Fig. 8. The pins 59 being threaded into the brackets 56 may be adjusted longitudinally to permit free rotation of the shaft 55 but substantially no longitudinal movement, and lock nuts 60 threaded on the pins 59 may be employed to hold the pins 59 in such adjusted positions.

The ends of the magnetic shaft 55 carry magnetic vanes 62 and B3 clamped on reduced diameter ends thereof by nuts 64, and these vanes are spaced to magnetically coact with the outer vertical edges of the pole pieces 9 and I0 respectively through small separating air gaps. The armature i! in this embodiment is, considerably shorter than the spacing of the vanes 62 and 63, both for the purpose of clearing these vanes and to minimize the magnetic effect between the vanes and the armature. A cam member 65 is suitably attached to the center of the shaft 55 which cam 55 engages an enlarged head of a screw 66 threaded into a forwardly extending arm 61 suitably attached to the armature l1, the screw 66 being locked in position by a nut 68.

A coil spring 69 is provided around the shaft 55 with a center loop engaging the lower edge of a forwardly extending arm 10 on the cam member 65, and the extreme outer ends of the spring 69 extend over the top of the shaft 55 toward the pole pieces 9 and ID with upwardly bent ends entering holes (not shown) in the top plate 'I I. The shaft 55 is thus biased in a counter-clockwise direction of .rotation. which direction of rotation is limited by a screw H threaded through the top plate H and locked by a nut 12 so that its lower end may engage the cam arm 10 when operated to its extreme upper position.

The manner in which the vanes 62 and 63 coact with the respective pole pieces 9 and I0 may be clearly seen from Fig. 7, or that is, these vanes are magnetically attracted upwardly against the force of the spring 69 to register more of their vertical surfaces with the outer surfaces of their respective pole pieces as the energization of coils l3 and M is increased, thereby rotating the shaft 55 in a clockwise direction in accordance with the degree of energization of the relay. The cam 65 is arranged as shown in Fig. '7 so that this clockwise rotation engages portions on its periphery with the head of the screw 66 which are of continuously increasing radii, thus forcing the armature I1 away from the pole pieces 9 and ID. The profile of the cam 65 is then arranged to at all times enforce an air gap between the armature I! and the pole pieces 9 and In which is in inverse proportion to the magnetomotive force prevailing between the pole pieces.

In order to retard the operation of the vanes in response to an abrupt change in magnetomotive force, two sleeves 13 are provided on the shaft 55 between the cam member 65 and the two vanes 62 and 63, which sleeves are of a non-mag- T netic current-conducting material. These sleeves 13 then act as a flux retarding choke means which opposes a rapid change in the value of flux flowing from one vane to the other through the shaft 55,but are comparatively ineffective to retard gradual flux changes.

The construction of the relay to which the modified compensating means shown in Fig. '7 and Fig. 8 has been applied has been considered to be the same as previously described, in connection with the other embodiments, but some modifications are obviously necessary such as the U-shaped armature-supporting bracket l8 (not shown in Fig. 8) which in this case must be made wider in order to clear the vanes 62 and 63, and also the inner vertical edges of the pole pieces 9 and Ill are preferably plain in Fig. 7 and Fig. 8 instead of concave as shown in Fig. 4.

Suitable contactsare of course to be operated by the armature l1 and such contacts are usually sufficiently flexed when engaging the associated upper fixed contacts so that the variations in position of the armature l1 as caused by the compensating means will not affect the resistance of the electrical circuit therethrough.

The edge of the cam 65 which contacts with the head of the screw 66 has been rounded as shown tore-duce the frictional resistance to the rotation thereof to a minimum.

The operation of the modified form of the present invention illustrated in Fig. '7 and Fig. 8

when applied to the railway track circuit of Fig.

1 is substantially the same as the other forms, or that is, when the track circuit current is adjusted by the variable resistor R to a value, which by flowing through the windings l3 and I4 produce a flux which reliably attractsthe armature average inter-rail leakage current, to produce a flux value which affords a. reliable armature release in response to a train shunt. The shaft 55 is of courseassuming an intermediate position when the adjustment of the screw 66 is being made because the normal degree of energization of coils l3 and I4 produces a flux flowing from one pole piece, through the associated vane, through the shaft 55, and to the other pole pieces through the other vane, which flux produces an upward attraction of the vanes 62 and 63 which is equally opposed by the spring 69 only at an intermediate position of the shaft 55.

The shaft 55 will now be rotated in either direction by an upward or downward movement of the vanes 62 and 63 in accordance with the gradual changes in the energization of coils l3 and M which may be caused by natural changes in the inter-rail leakage'current. The rotation of shaft 55 then varies the reluctance of the magnetic circuit by the cam 65 in such a proportion to the changes in the energization of coils i3 and M that the flux in the armature I1 is maintained at the value selected by the screw 66.

However when a train enters the track section, the energization of coils l3 and I4 is quickly decreased, but due to the flux retarding sleeves 13, the flux in the shaft 55 does not immediately decrease proportionally, and consequently the reluctance of the magnetic circuit is not effectively changed by a rotation of the cam 65 before the armature l1 drops away. A means for preventing a movement of the air gap regulating means while the armature I1 is dropped away has not been shown in this modified form, but it is obvious that an arm operated by the armature IT, as shown in Fig. 3, could operate in a similar manner to engage an extension of the vanes 62 and 63, forexample, and thus prevent rotation of the shaft 55 while the armature I1 is in its released position.

In all the forms of the present disclosure, it has been considered that the variations in the amount of flux passing through the compensating magnetic structures according to their rotated positions do not materially affect the amount of flux passing through the armature ll, except due to the effected change in air gap, but it is obvious that the flux path through the armature 31 or the shaft 55 is in multiple with the path through the armature l7, and in some cases, it may be found that a change in position of the compensating means materially affects the armature l'l apart from the air gap variation. However, it is contemplated that in this case, the only result would be an over-compensation which could be rectified by a change in tension of the springs 38 or 69.

A simple and compact relay has thus been provided which is particularly adaptable to normally energized circuits in which it is desirable to detect, with great certainty, an abrupt reduction in the energization thereof. Many of such'norrnally energized circuits are materially affected by changes in natural conditions, such as gradual variations in the electromotive force of the source of energy, and changes in the interrail leakage current in track circuits caused by varying weather conditions, and the present relay provides a means for detecting an abrupt reduction in the energization of such a circuit with equal certainty regardless of the natural conditions which had prevailed previous to such abrupt reduction. The manner in which the above operation is accomplished is particularly reliable and advantageous because the reliability of the energizing circuit is in no way impaired by the use of automatically variable resistors or the like, but rather a simple and positive means has been employed to regulate the reluctance of the relays magnetic circuit, thus preventing continued operation from altering the electrical characteristics of the energizing circuit in any manner.

The above rather specific description of the embodiments of the present invention is given solely by the way of example, and is'not intended, in any manner whatsoever, in a limiting sense. It is also to be understood that various modifications, adaptationsand alterations may be appliedto meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

Having thus described my invention, what I claim is:

l. A relay having in combination, a 'U-shaped magnetic structure, windings on the magnetic structure, amain armature attracted to a position magnetically joining the ends of the U- shaped magnetic structure When current above a predetermined value flows in the windings, a threaded shaft interposed between the armature and the magnetic structure whereby the proximity of the armature to the ends of the magnetic structure may be determined in accordance with the rotated position of the threaded shaft, a magnetic member carried by the threaded shaft and coacting with the ends of the U-shaped magnetic structure whereby to rotate the shaft, and an arm .on the armature operable to prevent rotation of theshaft while the armature is .1111 its unattracted position.

2; In a relay of the class wherein an armature is moved toward an electromagnet in response to a degree of energization of the electromagnet which is ,above a predetermined value and said armature is moved away from the electromagnet by a biasing means when the degree of energization of the electromagnet falls "below said pre-. determined value, the combination of, regulating means variably limiting the distance of movement of the armature toward the electromagnet inaccordance with the degree-of energization of the electromagnet, and means retarding the response of .the regulating means to abrupt changes in the degree of energization of the electromagnet.

3. In a relay of the class wherein an armature is held'toward an electromagnet in response to a degree of energizationof the electromagnet which is above a predetermined value and said armature is moved away from the electromagnet by a biasing means when the degree of energization of the electromagnet falls below .said predetermined value, the combination of regulating means variably limiting the movement of the armature toward the electromagnet in accordance with the degree of energization of the electromagnet, means retarding the response of the regulating means to abrupt changes in the degree of energization of the electromagnet, and locking means preventing operation of the regulating means while the armature .is operated away from the e'lectromagnet by the biasing means. i

l. Ina relay, an electromagnet having two extending pole pieces, an armature operable toward thepole pieces when current above a predeterminedvalue flows in the .electromagnet and operable away from the pole pieces bylgravitational force when said current falls below said predetermined value, and means .coacting with the pole pieces for variably separating the armature from the ,pole pieces in accordance with the amount of current in the electromagnets, the

operation of said means being delayed in response to changes in current in theelectromagnet which occur abruptly.

5. In a relay, an electromagnet having spaced extending pole pieces, a contact-operatingarmature positioned to magnetically-connect the pole pieces and to vary the reluctance of the magnetic circuit of the electromagnet in accordance With its proximity to the pole pieces, a rotatable armature positioned between the pole pieces and rotatable against a biasing spring to various positions in accordance with the magnetomotive force existing between the'pole pieces, and means enforcing a separation of the contact operating armature from the pole piecesin accordance with the position of the rotatable armature whereby the magnetic flux in the contact operating armature is maintained a constant value regardless of changes in the magnetomotive force of the electromagnet.

V 6. In a relay having electromagnetic structure including windings about spaced magnetic cores, the cores being magnetically joined at their upper ends and having enlarged pole pieces at their;

lower ends attached beneath a non-magnetic top plate; an armature operable toward and away fromthe lower surface of the pole pieces, a vertical shaft between the pole pieces and having a lower end engaging the armature with an upper end threaded into a holding member manually rotatable within the top plate, amagnetic member attached to the shaft and coacting'with'the vertical edges of the pole pieces in a manner to magnetically effect rotation of the shaft in one direction, a spiral spring actingv in opposition to the magnetic rotation of the shaft, a horizontal sectcrattached to theshaft, and an arm operated by the armature toward the edge of the sector when the armature is operated away from the pole pieces. V

7. In a relay having electromagnetic structure including windings about spaced magnetic cores,

direction, aspiral spring acting in opposition to the magnetic rotation of the shaft, a horizontal sector attached tolthe shaft, and an arm operated by the armature toward the edge vof. the sector when the armature is operated away from "the pole pieces.

8. In a relay having an electrom'agneti-cstructime including windings about spaced magnetic cores, the cores being magnetically joined at their upper ends and having enlarged pole pieces at their lower ends attached beneath a nonmagnetic topplate; an armature operable'toward and away from the' lower surface of "the pole pieces, a magnetic'sha ft rotatably carried by the top plate, rotatory biasing means acting on the shaft, magnetic vanes fixed to the ends of the shaft and coacting with the outer vertical surfaces of the pole pieces whereby the shaftisrotated .in oppositionto the rotatory biasing means in accordance with the magnetomotive force ob-' taining between the pole pieces, a cam operating to enforce a separation of the armature from the pole pieces in accordance with the rotated position of the shaft, and a non-magnetic current-conducting sleeve on the shaft whereby to retard the rotation of the shaft in response to an abrupt change in the magnetomotive force bethe pole pieces, means retarding the rotation of the shaft in response to an abrupt change in the strength of said magnetomotive force, and cam means on the shaft operating on the armature to thereby regulate the separation of the armature from the pole pieces in inverse proportion to gradual changes in the strength of said magnetomotive force. 1 V 10. In a relay wherein an electromagnet is normally energized to attract an armature toward pole pieces of the electromagnet, the combination of a magnetic shaft rotatably held in a definite relation to the pole pieces, magnetic vanes on the ends of the shaft coacting with the pole pieces in a manner to rotate the shaft, biasing means pposing such rotation of the shaft whereby the shaft is rotated to various positions depending on the strength of the magnetomotive force between the pole pieces, means retarding the rotation of the shaft in response to an abrupt change in the strength of. said magnetomotive force, cam means on the shaftoperating on the armature to thereby regulate the separation of the armature from the pole pieces in inverse proportion to gradual changes in the strength of said magnetomotive force, and means for manually adjusting the separation of the armature from the pole pieces which permits subsequent regulation thereof by the cam means. I

11. In a relay, two vertical magnetic cores joined at one end and having enlarged pole pieces at the other ends, a non-magnetic member-holding the cores, windings on the cores, an armature operable toward or away from the pole pieces in accordance with the degree of energization of the windings, a manually rotatable member in the core holding member, a shaft threaded into the manually rotatable member and engaging the armature when operated toward the pole pieces, and means for automatically rotating the shaft in accordance with gradual changes in the degree of. energization of the windings.

12. A relay having in combination, an electromagnet having an incomplete magnetic core, a contact operating armature operable to a position completing the core of the electromagnet, and magnetic means automatically providing a length of air gap between the armature and the core of the electromagnet which is in inverse proportion to the degree of energization of the electromagnet, wherebyto maintain a constant value of magnetic flux in the armature regardless of gradual changes in the degree of energization of the electromagnet.

13. In a normally energized track circuit, a relay energized by the track circuit current to hold a contact-operating armature in an attracted position when the track circuit is unshunted, a compensating armature in the relay movable to various positions in accordance with the degree of energization of. the relay, means operated by the compensating armature to move the contact-operating armature in a manner to maintain a constant flux in the contact-operating armature regardless of gradual changes in the normal energization of the relay, and means retarding the response of the compensating armature to an abrupt decrease in energization of the relay, whereby to permit the contact-operating armature to drop away in response to a shunt on the track circuit before the compensating armature eifectively moves in response to such shunt.

14. In a track circuit, a track relay, a first armature in the track relay attracted or released in accordance with the unshunted or shunted condition of the track circuit, and a second armature in the track relay regulating the attracted position of the first armature in accordance with gradual changes in the degree of energization of the track relay when unshunted, whereby to permit the release of the first armature in response to a shunt on the track circuit with equal certainty regardless of the prevailing ballast condition in the track circuit.

15. In a track relay, a first armature attracted or released in accordance with abrupt changes in the degree of energization of the relay, and a second armature regulating the attracted position of the first armature to maintain a constant flux density in the first armature regardless of gradual changes in the degree of energization of the relay.

16. In a track relay, an electro-magnet having extending pole pieces, an armature operable toward said pole pieces when current above a predetermined value flows in the electro-magnet and operable away from the pole pieces by gravitational force when said current falls to a predetermined lower value, slow acting adjusting means for variably separating the armature from the pole pieces when in its attracted position in accordance with gradual changes in the potential across said electro-magnet, and means for looking said adjusting means upon dropping of said armature. I 1'7. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on the core, an armature biased to a position away from the pole pieces and movable toward said pole pieces in response to magnetic flux created by current supplied to the winding, a magnetic shunt path including a magnetizable member movable to different positions relative to said pole pieces for regulating the flux which passes through the armature in response to variations in the magnitude of the current supplied to the winding, and means controlled in part by said armature for governing the position of said member.

18. In a relay, a magnetic core structure terminating in two pole pieces, a winding mounted on said core, an armature mounted for movement relative to said pole pieces in response to magnetic flux created by current supplied to said winding, an auxiliary magnetizable member mounted for movement relative to said pole pieces in response to such magnetic flux for regulating the flux through the armature in response to variations in the current strength supplied to the winding, a biasing device for governing the position of said member when influenced by the flux, and means controlled by said armature operative 8' area-r90:-

when the armature is released in. response. to. de'energizing the winding to retain. said auxiliary member at the position. to which it was moved by the magnetic. flux;

19. In combination, a section of railway track, a source of. current connected across: the rails of: said section, an electromagnet receiving current from. said rails and having an armature adjusted for operation when the magnetic flux acting thereon is that created by a predetermined value of current, amovable magnetizable member operable to: different positions relative to the core structure of the electromagnet for regulating the flux which passes through said armature to reduce in the. armature the. flux created by currents greater than said predetermined value, and means controlled in part by the posi-- tion. of said armature for governing. the position of said member.

20. In a relay; a: magnetic, core structure terminating in twopole pieces, a winding mountedon said core; an armature mounted for movement. relative to said pole pieces in response to: magnetid flux created by current supplied to said winding, a magnetic shunt path including a magnetizable member mounted for magnetic relationship with said pole pieces for regulating the magnetic flux through the armature when current above a predetermined value is sup-plied to the Winding, and a short-circuited winding mounted on the shunt path for delaying the dying away and the building up of flux through said shunt path.

21. In combination, a section of railway track, a source of current connected across the rails of said section, a track relay receiving current from said rails and adjusted for release of its armature at a predetermined value of current,

a movable magnetizab-le member mounted for movement relative to the pole pieces of the relay by flux flowing in multiple with said armature, and means to associate movement of the member with movement oithe armature whereby a-v gradual change in the ballast resistance of the. section automatically changes the setting of the member but a sudden decrease in the energizing current to release the: armature causes the member to be retained in its former setting.

22. A relay of the direct current. tractive type for use with track circuits on railroads com,- prising, a magnetic core structure forming two. spaced po lepieces, a winding on said core structure, a main contact operating armature biased for movement away from said pole pieces and and responding to variations in the. current in said winding, spring means for biasing said auxiliary armature with a force varying with its position toward a position for maximum reluctance of said. shunt path, said auxiliary armature' assuming, different positions in its magnetic shunt path dependent upon the strength of the current in said winding, and means actuated by movement of said main armature to its rctracted position for retaining said auxiliary armature in its then existing position.

23., A relay of the direct current tractive type for use on railroads comprising, a core structure and a winding for attracting a biased movable armature. to open. and close contacts, a magnetic movable member disposed in a magnetic flux path in shunt with said armature, spring means for biasing said member to a position for the maximum reluctance of said shunt path, said member being moved inv opposition to said spring means by variations in the current flowing insaid winding; to different positions dependent upon the: magnitudeof such. current, means associated with said movable member for delaying a change in its position in response to a change in the current in. said winding, and means responding to the movement of said armature toitsretracted. position for retaining said member in the position existing at the time said armature assumes its retracted position.

24-. In av relay of the type described, a magnetic core structure terminating in two spaced pole pieces, a winding on said core structure, a mainmovable armature attracted toward said pole pieces bythe magnetic flux in said core structure produced by current flowing in said winding, means including a.- biased movable auxiliary armature disposed in a magnetic flux path in shunt with said main armature for varyingthe flux passing through said main armature depending 

